Over the next few decades, climate change could turn Wisconsin into a very different looking place. Winters will be shorter, warmer and rainier. Our northern forests could undergo a visible transformation, hosting an unfamiliar mix of trees. Trout streams could seriously decline, and aquatic and terrestrial ecosystems across the state could be disrupted in ways that favor invasive species over native plants and animals.

Climate change poses a growing challenge for Wisconsin's landscapes, waters, fish and wildlife. Managing our natural resources and maintaining the outdoor look and feel of our state will be increasingly complex in the years ahead.

"We need to think about what climate change means for our natural resources and get out ahead of this problem, and we're working hard to do that," says Jack Sullivan, who directs DNR's Bureau of Science Services. Sullivan coordinates efforts to evaluate how changing climate will alter the agency's management responsibilities and what strategies could minimize those changes.

He's also a key participant in the Wisconsin Initiative on Climate Change Impacts, or WICCI. Founded by the Department of Natural Resources and the Nelson Institute for Environmental Studies at the University of Wisconsin-Madison, WICCI has grown into a broad statewide project with more than 250 participants from the public and private sectors. The researchers lend their expertise to working groups that are preparing strategies for dealing with the consequences that climate change poses for soil conservation, water resources, public health, agriculture, coldwater fisheries, stormwater management, wildlife, coastal communities, forests and other plant and animal communities in Wisconsin.

WICCI's first objective was to characterize Wisconsin's future climate. UW-Madison climate scientists, using data from the world's most powerful computer models, estimate that average annual temperatures in Wisconsin will continue to rise approximately six to seven degrees Fahrenheit by midcentury. According to their projections, an even greater percent of the warming will occur in winter. Growing seasons will be longer and summers will be hotter. Wisconsin will likely receive more total precipitation, especially in winter, spring and fall, and rainstorms are likely to be more intense (for a more detailed description, see our previous story Preparing to Adapt, in the February 2010 issue, or visit Wisconsin Initiative on Climate Change Impacts.

Impacts on Wisconsin's water resources

One of the earliest and clearest signs of recent climate change can be seen in records of ice cover on Wisconsin lakes, which have been kept for more than a century.

"The annual duration of ice on Lake Mendota in south central Wisconsin has declined by a full month, or 25 percent, over the past 150 years. Lakes across the state show a similar trend," says UW-Madison limnologist John Magnuson, who co-chairs the committee that oversees WICCI research. "Ice cover is a sensitive indicator or ‘miner's canary' that reveals that climate change is already underway in Wisconsin."

Less ice also means shorter ice fishing seasons and has negative consequences for businesses and communities that bank on winter recreation.

WICCI's Water Resources Working Group also assessed an array of other potential climate change impacts on water levels. Lake levels have been lower in northern Wisconsin in recent years due to a prolonged drought; these droughts have occurred periodically during the past century, but warmer temperatures, reduced ice cover and increased evaporation rates could intensify the effects of drought on lakes and wetlands.

In other parts of the state, increased precipitation – both in overall amounts and in more intense rainstorms – is expected to push lake levels higher, and runoff from heavier seasonal rains could carry more sediment and nutrients into lakes.

Loss of fish habitat

Fish habitat in rivers and streams could also be affected by rising water temperatures, changes in groundwater recharge rates and an increase in runoff from heavy storms. For example, Wisconsin is at the southern edge of the natural distribution of brook trout, a native coldwater fish. An increase in the average summer air temperature of just over 5° F could eliminate up to 95 percent of the brook trout habitat across the state.

Scientists in the group modeled how 50 common stream fish species would respond to three different climate change scenarios. Twenty-three species were predicted to decline, with one coldwater (brook trout) and four coolwater species projected to vanish from the state's streams and rivers under a worst-case scenario. Northern pike and walleye would lose most of their habitat. Four warmwater species showed little change, but 23 are predicted to increase in range, including game fish such as channel catfish, smallmouth bass, largemouth bass and black crappie.

Nongame fish, including various minnows and darters, will also gain as Wisconsin's climate changes. However, WICCI experts say fishery losses will far outweigh these gains; most of the coldwater streams that will likely become warmer are too small to host warmwater game fish.

Other wildlife will also be affected as stream temperatures rise. Wisconsin is one of the few remaining states where the Hine's emerald dragonfly, a federally endangered invertebrate, is found. The dragonfly's larvae can only develop in ephemeral cool springs. If these waters warm or increased rainfall prolongs wet conditions, the insect may go extinct.

Pressure on plants and animals

Many other state animals and plants could be harmed by climate change. As winter temperatures continue to warm, Wisconsin will see more precipitation falling as rain rather than snow, resulting in fewer days with snow cover. That threatens species that are adapted to and rely on snow cover for their winter survival. Climate scientists project that snow cover will drop by 40 percent in northern Wisconsin over the next half century. Snow is both a source of moisture and a thermal insulator for the fragile root systems of lowland conifers. Some wildlife, such as the American marten and voles, rely on layers of snow for insulation and protection from predators. A reduction in snow depth will subject martens and small mammals to greater risks of predation as well as more competition for food.

Statewide, reduced snow cover will increase opportunities for white-tailed deer to forage, resulting in more browsing damage to native vegetation, forests and croplands. Other animals that could benefit from climate change include the gray squirrel, European starling and Canada goose.

As Wisconsin winters become milder, spring will continue to arrive earlier, a trend already evident in the state. Spring weather arrives six to 20 days earlier than it did in 1950, extending the growing season by two weeks. Trees are budding and flowers are blooming sooner.

This earlier onset of spring and lengthening of the growing season will affect the timing of life-cycle events of plants and animals. Some respond to temperature as a cue to initiate growth and reproduction; others to length of day or to each other's life-cycle cues. These relationships may be thrown out of sync as the climate continues to change.

In addition, changes in the timing of flowering caused by earlier spring arrival may disrupt interactions with insect pollinators. For example, some spring flowers are opening earlier than in the past, when the flies and bees that pollinate them may not yet have hatched. In the southern upland forests, the suite of ephemeral flowers like trout-lilies, trilliums, violets and bloodroot growing on the forest floor is likely to be moderately to highly affected by climate change because of interference in pollination. These flowers bloom and drop their seeds before the forest canopy has formed its leaves. They have a very short window for reproduction, and alterations in the timing of pollination caused by climate change may adversely affect these species.

Wildlife migration behavior is also shifting in response to earlier snowmelt, warmer temperatures, more precipitation and other signals. In a recent study by Nina Leopold Bradley and others, researchers noted a shift in the phenology of 17 species in the state. The Canada goose now arrives a month earlier than in the 1930s and is a year-round resident in southern portions of the state, in some cases degrading water quality and damaging crops.

Another chain of climate impacts might be seen at ground level. A warmer climate will likely lead to a reduction in soil moisture. Hotter days – and more of them – will mean more water evaporation from the soil. Amphibians such as the American toad and eastern tiger salamander rely on humidity and moisture in the soil to maintain the water balance in their bodies.

Drier soils can reduce plant vigor and overall vitality; trees and other plants need this moisture to regenerate, and reduced soil moisture will make it more difficult for many plants to replace damaged cells. Forests such as the conifer lowlands – wet, boggy areas dominated by trees such as tamaracks, black spruce and white cedar—depend on very moist soils. A reduction in soil moisture would threaten these forests and potentially change the types of plants that grow in those regions.

Forest migration

Northern Wisconsin hosts a number of plant species that are at the southern edge of their natural ranges. If temperatures continue to rise, those ranges will shift northward out of the state, and plants currently growing in states to our south will expand into southern Wisconsin.

Furthermore, a warming climate will put pressure on boreal forest species. Birds and invertebrates within this ecosystem will be forced northward, followed by tree and plant species. By the end of the century, trees such as aspen, white birch, black spruce and balsam fir might find suitable remnant habitat only in northern Minnesota or the upper peninsula of Michigan instead of in Wisconsin.

Tamarack lowlands are particularly at risk because they persist at the southern extent of their range and are sensitive to reduced snow cover, which could allow their roots to freeze without the insulating blanket of snow.

In addition, many of the invasive tree species in Wisconsin are opportunists and will probably be well adapted to grow in warmer temperatures and a carbon dioxide enriched atmosphere. Their ability to rapidly colonize disturbed sites will afford these plants an advantage in areas where floods, droughts and tree mortality open up growing space.

Some native trees and other plants will benefit from warmer weather. Hardwoods such as hickory, black oak and black walnut, might be winners in a warmer Wisconsin, expanding their range within the state as temperatures rise.

Increasing resilience through adaptation

esigning and carrying out strategies that minimize the impacts of climate change will test natural resource managers in the years ahead. Wisconsin has taken its first steps on that path through the efforts of WICCI. While many of the working groups are in the early stages of developing strategies, a number of ideas and recommendations have already taken shape to build resilience in Wisconsin's natural resources.

Improve models relating the interactions of weather, soil hydrology, groundwater hydrology, and groundwater discharge to streams and use these models to evaluate vulnerable resources.

Establish and maintain corridors of contiguous habitat to provide for animal migration.

Relocate some plants and animals in anticipation of projected climate change.

Build stronger relationships with the public to enhance knowledge of ecological communities.

These are but a few of the preliminary ideas WICCI participants are developing to meet the growing challenge of climate change to Wisconsin's natural environment. It's a good start on what is sure to be a long-term endeavor.

Steve Pomplun directs community and alumni relations for the Nelson Institute and coordinates outreach for the Wisconsin Initiative on Climate Change Impacts (WICCI). Richard Lathrop is a DNR research limnologist and co-chair of the WICCI Science Council. Alison Coulson is the WICCI program manager and an outreach specialist at the Nelson Institute. Elizabeth Katt-Reinders is lead author of the WICCI report and a DNR publications editor.

Read more about WICCI findings

A new WICCI report explores an array of potential consequences as our state's climate becomes warmer and wetter. The report offers strategies to help both human and natural systems adapt. "Wisconsin's Changing Climate: Impacts and Adaptation," will be published this month and is available online at Wisconsin Initiative on Climate Change Impacts.

The report covers a wide range of topics from coldwater fisheries, forests and wildlife habitat to stormwater management, agriculture and human health. It is the first in what is expected to be a series of reports that will be issued every four to five years.

"This report is the first comprehensive survey of climate change impacts in Wisconsin, and it provides information that will help decision makers begin to plan for the kinds of changes we're likely to see in the years ahead," says Lewis Gilbert, associate director of the Nelson Institute and a WICCI council member.